194 Life History of Wit^eivorms 



The Egg. 



Generally broadly ovoid, but irregular in both shape and size. Average 

 dimensions of four ova -59 mm. x -47 mm. A fifth measured after 

 fixation -64 x -40. Shell transparent, exhibiting the milky-white yolk 

 and embryo within. The germinal band of the embryo appears as a 

 yellowish-green stripe. The surface of the shell is almost smooth, though 

 a few irregular shallow punctures are visible under the microscope. 



First Larval Instar. 



The young larva on hatching is about 2-5 mm. in length and less than 

 •4 mm. in breadth across the prothorax. It is milky white in colour, 

 shining, but w^hen examined under the microscope is found to be minutely 

 punctured and wrinkled. It has the general appearance of being broader 

 and more stumpy than the later stages. Only the mouth parts are yellow, 

 the mandibles being darker still and quite brown at their apices. The 

 9th abdominal segment is pointed and somewhat constricted at about 

 two-thirds of its length. All the setae are colourless, the eye spots black. 

 The head and all the body segments, with the exception of the 9th and 

 10th abdominal segments are broadest in the middle and somewhat 

 rounded at the sides. The cauda and margins of the sensory pits of the 

 9th abdominal segment are colourless, so that the latter are difficult to 

 make out in life. The marginal striae at the base of the body segments, 

 though present, are also only to be made out with difficulty. 



Throughout the first instar the larva remains pale and semitrans- 

 parent, though at the end its general colour has become faintly yellow. 

 The margins of the sensory pits on the 9th abdominal segment are then 

 visibly brown, the constriction near the end of the same segment has 

 been lost and the anterior half of the segment has its sides subparallel, 

 while the posterior tapers to a point at the cauda, which is still colourless 

 or almost so. Five larvae taken from the pots at this age measured 

 3-25-3'5 mm. in length. 



The following points may also be noted in which the young larva 

 of the first instar differs in greater or less degree from the full-fed 

 larva. 



Sides of the head subparallel. It is broader than long, measuring the 

 breadth across the middle and the length from the insertion of the man- 

 dibles to the base of the head. 



Instead of the three-pronged nasale or clypeal process, the latter is 

 represented by a single-toothed process, twice as broad as long and blunt 

 at the apex (Fig. 2 e). 



